1. Field of the Invention
The present invention relates to a spark plug, and more particularly to a spark plug that can protect a discharge spark.
2. Description of the Relative Art
A motorcycle or gasoline vehicle's engine is equipped with spark plugs to ignite fire and generate power. Generally, when spark plugs form a high discharge voltage, the engine introduces air via an intake manifold to form a fuel-air mixture into a cylinder almost at the same time, and generates power by igniting fuel-air mixture by discharge spark. However, the forms of the spark plug are different according to engine's design.
FIG. 1 shows a conventional spark plug 10. As shown in FIG. 1, the spark plug 10 includes a housing 12, a ceramic insulator 14, and a central electrode 16. One end of the housing 12 extends and forms a ground contacted electrode 18. The ground contacted electrode 18 is perpendicular to the central electrode 16 and is apart from the central electrode 16 with a gap 24. The gap 24 is where a high voltage discharge spark formed (not shown). Besides, the other end of the spark plug 10 covers by an insulator 20 for preventing a short circuit or electric leakage. The insulator 20 further connects to a connecting head 22. The ceramic insulator 14 may enclose a sealing material such as aluminum oxide and a seal ring between the ceramic insulator 14 and the housing 12 in assembly such that the ceramic insulator 14 and the housing 12 may form an air-seal structure for preventing pressure from leaking out from the engine while assembles the housing 12.
Referring to FIG. 2, the conventional spark plug 10 is disposed on an engine 30, and a discharge spark 26 forms between the central electrode 16 and the ground contacted electrode 18. When fuel-air mixture 40 enter into a combustion chamber 32 and the piston 34 go up to Top Center Point, the air fuel mixture 40 ignites by the exposed discharge spark 26 in the combustion chamber 32 of the engine 30 directly, thereby drives a piston 34 of the engine 30 to generate power. However, when stepping on the gas pedal heavily to speed up suddenly or other circumstances, a large amount of high pressure fuel-air mixture 40 will enter into the combustion chamber 32 speedily and breach the discharge spark 26. Therefore, the discharge spark 26 may snuff out and affect the ignited efficiency of the spark plug 10, such that causes the moving motorcycle or vehicle cannot speed up smoothly.